Thermoplastic elastomer compositions are well known. Such compositions have a high melt flow property that allows them to be processed as thermoplastic materials, yet they also demonstrate certain rubbery characteristics.
U.S. Pat. No. 3,037,954 teaches a process to prepare a thermoplastic elastomer in which polypropylene and a rubber are subjected to "dynamic curing conditions". The examples of the patent illustrate that the products produced according to the patent demonstrate the properties of thermoplastic elastomers.
Simple blends of carboxylated nitrile rubber and polyvinyl chloride are also known. The blends are somewhat thermoplastic and are used in many molding applications. However, these blends do not typically exhibit the balance between rubbery properties and thermoplastic properties which is characteristic of thermoplastic elastomers.
More recently, flux blends of carboxylated nitrile rubber, polyvinyl chloride and nylon have been developed, as disclosed in U.S. Pat. No. 4,438,230. Vulcanizates of these blends are especially useful in applications where high tensile strength and retention of properties after ageing are required. The vulcanizates are somewhat rubbery, as illustrated by their relatively low compression set, but they do not exhibit the high melt flow of a thermoplastic.
It is an object of the present invention to provide a process to prepare an oil resistant, thermoplastic elastomer composition having a good balance between compression set and melt flow index properties.